The MPID Center for membrane protein structure determination is focused on an important biological and medically relevant theme. It aims to determine the structures of membrane proteins involved in pathogenesis, with a focus on viral membrane proteins, bacterial membrane proteins, and human membrane proteins involved in pathogenic pathways. Membrane proteins represent >60% of all drug targets and they are also key players in the pathogenesis of infectious diseases. A critical step for the elucidation of the complex processes that are catalyzed by membrane proteins is an understanding of the structure, dynamics and function of membrane proteins. Our knowledge of processes catalyzed by membrane proteins suffers mainly from the lack of information concerning their structure as less than 300 different membrane protein structures are known at present. The Center targets membrane proteins of important viral and bacterial pathogens, their infectious pathways, and molecules involved in host defense against the pathogens. This theme is unique and the results and structures determined by the Center will be highly relevant for human health worldwide. The structure determination of each of the targets may provide important clues for the understanding of the infectious disease pathways and can therefore form the basis for the treatment and prevention of infectious diseases. The major goal of the Center is to use the biological theme of membrane proteins in infectious diseases as the basis for the determination of more than 40 novel membrane protein structures and to develop new technology for high throughput membrane protein expression, isolation, functional characterization, crystallization, and structure determination. Therefore, the Center aims to significantly contribute to the main goal of the PSI structure initiative by solving structures of novel membrane proteins with a large sequence and structural coverage. The Center also aims to develop new bioinformatics tools for the analysis of potential targets, solved structures, and the prediction of membrane protein structures. The MPID center will also collaborate with the community and the PSI on the structure determination of target membrane proteins that complement the initial targets of the center.